Stable fuel oil



Patented June 24, 1941 STABLE FUEL 01L William J. Ryan, Wilmington, and Marcus T. Kendall, Long Beach, Calif., assignors to The Texas Company, New York, N. Y., a corporation of Delaware N Drawing. Application March 22, 1939, Serial No. 263,400

6 Claims.

This invention pertains to fuel oil derived from petroleum residues containing a substantial proportion of colloidal, carbonaceous material, and to the preparation of such fuel oil in a relatively stable form.

The invention broadly contemplates a stable fuel oil prepared from petroleum residues, such as obtained in the cracking of paraffin and mixed base crudes, containing colloidal, carbonaceous material which precipitates in storage or upon moderate heating, by incorporating in said residues a substantial proportion of highly naphthenic and aromatic hydrocarbons sufhcient to prevent precipitation of this colloidal carbonaceous material.

It is customary practice in the refining of paraffin and mixed base crude petroleum to subject the crude to non-destructive distillation for the purpose of distilling gasolene, kerosene, gas oil constituents, etc., from the crude. mainin-g residuum may then be subjected to relatively mild cracking or viscosity-breaking for the production of naphtha, gas oil, and low viscosity fuel oils. When the residuum is thus subjected to cracking thehigher boiling point paraffin hydrocarbons are decomposed into lower boiling point hydrocarbons and at the same time a substantial amount of colloidal, carbonaceous matter is produced.

Upon standing in storage substantial pre- :3 cipitation of this carbonaceous matter occurs.

Furthermore, when this cracked fuel oil is preheated, prior to combustion in furnaces, a considerable precipitation of the carbonaceous material occurs, with the consequent deposition of the material upon the interior surfaces of the preheating apparatus.

Thus, it is customary practice when employing fuel oil in furnaces to preheat the oil in suitable heaters at a temperature of around 180 to 200 F. As a result of such heating the oil becomes more fluid and, as a result, precipitation of this carbonaceous material is facilitated. The deposition of this precipitated material upon the interior surfaces of the preheating apparatus seriously interferes with the satisfactory and efficient use of the preheating apparatus and frequently interrupts the operation of the furnace.

We have discovered that the precipitation of this colloidal, carbonaceous material, inthe case of cracked fuel oils obtained from paraffin and mixed base crudes, can be substantially inhibited by blending with the cracked fuel oil a suitable proportion of heavy naphthene hydro- The recarbons such as are obtainable from naphthene base crude. By paraffin, mixed base, and naphthene base crudes We contemplate crudes classified according to the method of classification described in the Bureau of Mines Bulletin R. I. 3279 by Lane and Garton, September, 1935.

Naphthene hydrocarbons suitable as a blending agent may comprise a distillation residue resulting from either the destructive or nondestructive distillation of naphthene base crude. The heavy naphthenic and aromatic compounds present in the fuel residuum produced in the drastic cracking of certain paraffin and mixed base crudes have also been found effective as inhibiting the precipitation of carbonaceous material contained in fuel residua produced in the relatively mild cracking or viscosity breaking of cracked petroleum.

The blending agent may be added to the cracked fuel oi1 containing carbonaceous matter in the proportion of about 2%) or by volume, although the proportion so added may be either smaller or larger, depending upon the nature of the oil to be stabilized.

It is also contemplated that the blending of the naphthene hydrocarbons with the paraffin hydrocarbons may be done either before or after the cracking operation.

The invention will be described further with reference to the following examples:

A Santa Fe Springs or Signal Hill crude was distilled in the conventional manner to produce a fuel residuum. This residuum was then charged to a pressure pipe still for the purpose of producing naphtha, gas oil and low viscosity fuel oil. In this operation about 7% of cracked gasoline, of gas oil, and approximately 62% of fuel oil were produced. When using this fuel oil as a furnace fuel it was found that during passage of the fuel oil through the preheaters, wherein it was heated to a temperature of around E1, rapid deposition of carbonaceous matter upon the interior surfaces of the preheater tubes occurred.

However, when this fuel oil was blended with approximately 25% by volume of a fuel oil obtained by subjecting Midway-Sunset light crude to mild cracking or viscosity breaking, deposition of the carbonaceous material within the preheater tubes was entirely prevented.

In another example a fuel residuum produced in the non-destructive distillation of Signal Hill crude was cracked in a pressure pipe still to produce a fuel oil residuum having a Saybolt furcl viscosity of 209 seconds at 122 F, This cracked residuum was blended with gas oil produced in the pipe still distillation so as to produce a blended fuel oil having a Saybolt furol viscosity of 25 seconds at 122 F.

After several weeks in storage this fuel oil revealed a substantial precipitation of carbonaceous matter, 1. e., about 2.5%, as determined by the ordinary centrifuge test for settlings.

By blending this fuel oil with 20% by volume of a cracked residuum produced when subjecting Midway-Sunset light crude to viscositybreaking, 90% of this carbonaceous matter was re-dissolved, so that the centrifuge test for settlings indicated a precipitation of less than 0.3%. A centrifuge test on the cracked residuum from Midway-Sunset light crude, prior to blending, indicated a precipitation of about 0.1%.

While the foregoing examples describe the employment of a blending agent prepared from naphthene base crude, it is contemplated that a suitable blending agent possessing somewhat similar characteristics as an inhibitor for the precipitation of carbonaceous material, may be produced from other sources. For example, a mixed base crude may be topped to approximately 60 to 150 seconds viscosity at 122 F. Saybolt furol. This residuum, containing mostly parafiin hydrocarbons, is then subjected to drastic cracking, so that some of the hydrocarbons in the residuum will be converted into naphthene, olefin and di-olefin hydrocarbons.

This mixture, or fractions thereof, is suitable as a solvent for the asphaltic or carbonaceous material which precipitates, or tends to precipitate, from the residues produced by subjecting parafiin base hydrocarbons to relatively mild cracking.

As already mentioned, blending may take place prior to cracking. For example, a residue pro duced by topping paraffin or mixed base crude may be blended with about 20-30% by volume of either a cracked or non-cracked residue derived from naphthene base crude. This blend may then be subjected to cracking, either mild or drastic. The fuel oil residues resulting from the cracking of this blend will be of stable character and one from which substantially no precipitation of colloidal, carbonaceous material will occur in storage or upon heating to moderate temperatures, such as around 200 or 309 F.

It is also contemplated that the stabilizing, highly aromatic oil may be either a naphthene base petroleum residue or a suitable fraction thereof, advantageously, of about the same viscosity as the parafim or mixed base fuel oil in which it is to be incorporated.

While we have indicated that the purpose of our invention is to stabilize certain fuel oils so as to prevent deposition of carbonaceous matter, either in storage at normal temperatures or upon heating in a fuel oil heater, we have found that the inhibited fuel oil of our invention continues to exhibit this freedom from carbonaceous deposition under ordinary conditions of storage or use even though such oils are subsequently diluted in the usual proportions with lighter fuel oils or gas oils. In other words, the inhibiting effect is not destroyed by reducing the viscosity of the inhibited oil to the lower viscosity commercial fuels by blending, as above explained.

We have also found that increasing the severity of cracking in the case of naphthene base residua results in increasing its effectiveness as an inhibitor. This is shown, for example, by the fact that blending approximately equal volumes of mildly cracked or viscosity-broken paraffin or mixed base residuum and a non-cracked naphthene base residuum produces a stable fuel mixture.

In the case of a mildly cracked naphthene base residuum the mixture, consisting of 60% paraflin or mixed base residuum and 40% naphthene base residuum, provides a stable mixture. However, if the naphthene base residuum has been subjected to drastic cracking the proportion of such naphthene base residuum may be reduced to 0% of the mixture and still produce a stable mixture.

In speaking of a mildly cracked or viscositybroken residuum, we contemplate, for example, one having a Saybolt furol viscosity of 200 seconds at 122 F. By drastically cracked naphthene base residuum we contemplate, for example, a fuel oil of about 350 Saybolt furol seconds at 122 F.

A typical commercial fuel oil mixture formed from such mildly cracked or paraffin mixed base residuum and drastically cracked naphthene base residuum comprises a blend of about 68% mildly cracked residuum, 20% drastically cracked naphthene base residuum, and 12% by volume of gas oil having a viscosity of about 40 Saybolt universal seconds at 100 F.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. As a composition of matter a stable fuel oil having a Saybolt furol viscosity of 25 seconds and above at 122 F. comprising a heavy viscous fuel oil residue produced in cracking a hydrocarbon selected from the group of hydrocarbons consisting of paraffin base and mixed base petroleum hydrocarbons, said residue containing colloidal, carbonaceous material which precipitates therefrom in storage and upon moderate heating, blended with around 20 to 49% by volume of naphthene base petroleum hydrocarbons of about the same viscosity as said residue and suflicient to inhibit substantial precipitation of said carbonaceous material.

2. As a composition of matter a stable fuel oil having a Saybolt furol viscosity of 25 seconds and above at 122 F. comprising a major proportion of a heavy viscous fuel oil residue produced in cracking a hydrocarbon selected from the group of hydrocarbons consisting of parafiin base and mixed base petroleum hydrocarbons, said residue containing colloidal, carbonaceous material which precipitates therefrom in storage and upon moderate heating, blended with a minor proportion of a naphthene base petroleum fraction of about the same viscosity as said residue and suflicient to inhibit substantial precipitation of said carbonaceous material.

3. As a composition of matter a stable fuel oil comprising a major proportion of a fuel oil residue produced in cracking a hydrocarbon se lected from the group of hydrocarbons consisting of para-inn base and mixed base petroleum hydrocarbons, said residue having a Saybolt furol viscosity of greater than 25 seconds at 122 F. containing colloidal, carbonaceous material which precipitates therefrom in storage and upon moderate heating, blended with a minor proportion of a heavy fuel oil of about the same 'viscosity produced in the cracking of naphthene base petroleum hydrocarbons.

4. The method of preparing stable fuel oil from the residue derived in cracking a hydrocarbon selected from the group of hydrocarbons consisting of paraffin base and mixed base crudes, and containing colloidal, carbonaceous matter which comprises blending said residue having a Saybolt furol viscosity greater than 25 seconds at 122 F, with about 20 to 40% by volume of heavy hydrocarbons of about the same viscosity derived from naphthene base crude, and in amount suiricient to prevent substantial precipitation of said carbonaceous matter from the oil during storage and upon heating to moderate temperatures.

5. As a composition of matter a stable fuel oil comprising a major proportion of a fuel oil residue produced in cracking a hydrocarbon selected from the group of hydrocarbons consisting of paraffin base and mixed base petroleum hydrocar- Icons, said residue having a Saybolt furol viscosity greater than 25 seconds at 122 F., containing colloidal carbonaceous material which precipitates therefrom in storage and upon moderate heating, blended with a minor proportion of heavy naphthenic hydrocarbons of about the same viscosity.

6. As a composition of matter a stable fuel oil comprising a major proportion of a fuel oil residue produced in cracking a hydrocarbon selected from the group of hydrocarbons consisting of paraffin base and mixed base petroleum hydrocarbons, said residue having a Saybolt furol viscosity greater than 25 seconds at 122 F., containing colloidal carbonaceous material which precipitates therefrom in storage and upon moderate heating, blended with a minor proportion of heavy aromatic. hydrocarbons of about the same viscosity.

WILLIAM J. RYAN. MARCUS T. KENDALL. 

